TRAFFIC CONTROL DEVICES 

GENERAL DISCUSSION

The purpose of traffic control at highway-rail grade crossings is to permit safe and 

efficient operation of rail and highway traffic over such crossings. Highway vehicles 

approaching a highway-rail grade crossing should be prepared to yield and stop if necessary 

if a train is at or approaching the crossing. 

PASSIVE DEVICES

A passive highway-rail grade crossing is described as follows: 

All highway-rail grade crossings having signs and pavement markings (if 

appropriate to the roadway surface) as traffic control devices that are not 

activated by trains. 

The following tables describe a variety of devices that can be used at a passive 

controlled highway-rail grade crossing, or supplement active devices. Table 5A are devices 

currently referenced in the 2000 MUTCD edition. Table 5B lists devices that are not currently 

proposed in the MUTCD, and any jurisdiction wishing to use these devices to experiment 

must request permission from the FHWA. 

15 
TABLE 5A - CURRENT MUTCD DEVICES 

MUTC Traffic Control Application or Indication of Need

R15-1 CROSSBUCK 

sign

Required device 

R15-2 “Multiple Tracks” sign Standard device, with 2 or more tracks; optional with gate. 

W10-1 Advance warning 

sign

Required device, with MUTCD exceptions 

RR Pavement 

Markings

All paved roads, with MUTCD exceptions 

R1-1 STOP sign As indicated in MUTCD reference 1993 memorandum.

W3-1, 

1a

STOP AHEAD 

sign

Where STOP sign is present at crossing. 

R1-2 YIELD sign As indicated in MUTCD reference 1993 memorandum.

W3-2, 

2a

YIELD AHEAD 

sign

Where YIELD sign is present at crossing. 

R3-1, -

2

Turn Restriction 

sign * 

Use with interconnected, preempted traffic signals. Install on 

the nearby parallel highway to control turns toward the tracks.

R3-4 U-Turn Prohibition 

sign 

Use in median of divided highways at highway-rail grade 

crossings to inhibit turning vehicles from using the track zone 

for illegal movement as necessary.

R4-1, 

W14-3

DO NOT PASS 

sign

Where passing near the tracks is observed. 

R8-8 DO NOT STOP 

ON TRACKS sign 

Where queuing occurs, or where storage space is limited 

between a nearby highway intersection and the tracks. May 

be supplemented with a flashing light activated by queuing 

traffic in the exit lane(s) from the crossing. (See discussion on 

Queue Cutters Signals.)

R8-9 TRACKS OUT OF 

SERVICE sign

Applicable when there is some physical disconnection along 

the railroad tracks to prevent train using those tracks.

R10-5 STOP HERE ON 

RED sign

Use with pre-signal and/or Stop Line pavement markings to 

discourage vehicle queues onto the track.

R10-11 NO TURN ON 

RED sign 

Use with pre-signal and/or where storage space is limited 

between a nearby-interconnected traffic signal controlled 

intersection.

R15-3, 

W10-1 

EXEMPT sign School buses and those commercial vehicles that are usually 

required to stop at crossings are not required to do so where 

authorized by ordinance.

R15-4 Light Rail Transit 

Only Lane sign 

series

For multilane operations where roadway users might need 

additional guidance on lane use and/or restrictions. 

R15-5, 

5a 

DO NOT PASS 

Light Rail Transit 

signs

Where vehicles are not allowed to pass LRT vehicles loading 

or unloading passengers where no raised platform physically 

separates the lanes.

16 
R15-6, 

6a

No Vehicles on 

Tracks signs

Used where there are adjacent vehicle lanes separated from 

the LRT lane by a curb or pavement markings.

R15 -7, 

7a

DIVIDED 

HIGHWAY sign

Use with appropriate geometric conditions. 

R15-8 LOOK, 

Supplementary 

sign

3⁄4 Multiple tracks 

3⁄4 Collision experience 

3⁄4 Pedestrian presence 

W10-2, 

3, 4

Advance Warning 

Signs Series

Based upon specific situations with a nearby parallel highway. 

W10-5 LOW GROUND 

CLEARANCE 

CROSSING sign

As indicated by MUTCD guidelines, incident history or local 

knowledge. 

W10-8, 

8a 

TRAINS MAY 

EXCEED 80 MPH 

(130 KM/H) sign

Where train speed is 80 mph (130 km/h) or faster 

W10-9 NO TRAIN HORN 

sign

Shall be used only for crossings in FRA-authorized quiet 

zones.

W10-10 NO SIGNAL sign May be used at passive controlled crossings.

W10-

11, 11a 

Storage Space 

signs 

Where the parallel highway is close to crossing, particularly 

with limited storage space between the highway intersection 

and tracks.

W13-1 “Advisory Speed” 

plate 

3⁄4 May be used with any advance warning sign where 

appropriate, 

e.g. advance warning, humped crossing, rough crossing, 

super-elevated track or other condition where a speed lower 

than the posted speed limit is advised.

I-12 Light Rail Station 

sign

Used to direct road users to a light rail station or boarding 

location.

I-13, 

13a

Emergency 

Notification sign

Post at all crossings to provide for emergency notification. 

Dynamic 

Envelope 

Delineation, 

pavement 

markings

Where there is queuing or limited storage space for highway 

vehicles at a nearby highway intersection.. 

Signs on both 

sides of highway 

3⁄4 For extra emphasis 

3⁄4 Multi lane 

3⁄4 One-way roads 

3⁄4 Curved approaches 

Increased 

retroreflectivity on 

highway signs

3⁄4 Nighttime train operations. 

Roadway 

delineators, post-

3⁄4 Frequent inclement weather 

3⁄4 Crossing narrower than approach pavement 

17 
mounted on 

shoulders

3⁄4 Isolated crossings 

3⁄4 May be used as an alternative to illumination 

Flashing lights on 

signs 

and lighted signs 

3⁄4 Presence of competing stimuli, “visual clutter” 

3⁄4 Restricted sight distance to the crossing 

3⁄4 High speed highway traffic approach 

3⁄4 Isolated crossing 

3⁄4 Heavy volume or queued traffic in advance of the 

crossing 

Overhead signs 3⁄4 Multi-lane approach 

3⁄4 High speed highway approach 

3⁄4 If a sign cannot be placed on the roadside 

3⁄4 May be used as an alternative to the double signs 

Crossing 

illumination: 

3⁄4 Nighttime train operations 

3⁄4 Crossings are blocked for long periods 

3⁄4 Train speeds are low 

3⁄4 Nighttime collision experience 

3⁄4 Curved approach (vertical and horizontal curves) 

3⁄4 Frequent occurrence of fog or smoke. 

Stop and flag 3⁄4 Railroad option, but may be considered by traffic 

engineer. 

3⁄4 Combination of low train frequency, short trains, highvolume highway traffic, multilane highway 

TABLE 5B - NOT CURRENTLY PROPOSED IN THE MUTCD - EXPERIMENTAL 

DEVICES

SECOND TRAIN 

and other 

supplemental 

signs

3⁄4 Multiple tracks 

3⁄4 Collision experience 

3⁄4 Pedestrian presence 

Buckeye Among a number of special signs under current research. 

HIGHWAY-RAIL GRADE CROSSING (CROSSBUCK) SIGNS 

The MUTCD states, “The Highway-Rail Grade Crossing (R15-1) sign, 

commonly identified as the Crossbuck Sign, shall be retroreflectorized white with 

the words RAILROAD CROSSING in black lettering. As a minimum, one 

Crossbuck sign shall be used on each highway approach to every highway-rail 

grade crossing, alone or in combination with other traffic control devices. If 

automatic gates are not present and if there are two or more tracks at the 

highway-rail grade crossing, the number of tracks shall be indicated on a 

supplemental Number of Tracks (R15-2) sign of inverted T shape mounted below 

the Crossbuck sign in the manner and at the height indicated in the MUTCD.” 

18 
 

STOP and YIELD SIGNS

The Intermodal Surface Transportation Efficiency Act of 1991 (ISTEA) (Public 

Law 102-240; 105 Stat 1914; December 18, 1991) required that the FHWA revise 

the MUTCD to enable State or local governments to install STOP or YIELD signs 

at any passive highway-rail grade crossing where two or more trains operated 

daily. In response, the FHWA published a final rule in the Federal Register (57 

FR 53029), which incorporated the new standards into the MUTCD. This final 

rule, published in March 1992, was effective immediately. 

The FHWA and the FRA published a memorandum containing guidelines for 

when the use of STOP or YIELD signs is appropriate. According to the jointlydeveloped document, “it is recommended that the following considerations be 

met in every case where a STOP sign is installed: 1” 

1. Local and/or State police and judicial officials commit to a program of 

enforcement no less vigorous than would apply at a highway intersection 

equipped with STOP signs. 

2. Installation of a STOP sign would not occasion a more dangerous 

situation (taking into consideration both the likelihood and severity of 

highway-rail collisions and other highway traffic risks) than would exist 

with a YIELD sign. 

According to this memorandum, any of the following conditions indicate that 

the use of a STOP sign might reduce risk at a crossing: 

1. Maximum train speeds equal, or exceed, 48 km/h (30 mph). 

2. Highway traffic mix includes buses, hazardous materials carriers and/or 

large (trash or earth moving) equipment. 

3. Train movements are 10 or more per day, five or more days per week. 

4. The rail line is used by passenger trains. 

5. The rail line is regularly used to transport a significant quantity of 

hazardous materials. 

6. The highway crosses two or more tracks, particularly where both tracks 

are main tracks or one track is a passing siding that is frequently used. 

7. The angle of approach to the crossing is skewed. 

1 U.S. Department of Transportation; Federal Highway Administration; 

Federal Railroad Administration. 1993. Recommended Guidance for Stop 

and Yield Sign at Highway-rail Grade Crossings. Washington, DC. 3 p. 

[Attachment 2 to a July 8, 1993 memorandum from the Associate 

Administrator for Safety and Systems Applications, FHWA, and the 

Associate Administrator for Safety, FRA, to the FHWA Regional 

Administrators and the FRA Regional Directors of Railroad Safety.] 

19 
8. The line of sight from an approaching highway vehicle to an approaching 

train is restricted such that approaching traffic is required to substantially 

reduce speed. 

The memorandum also states, however, that the above conditions should be 

weighed against the possible existence of the following factors: 

1. The highway is other than secondary in character. Recommended 

maximum of 400 ADT in rural areas, and 1,500 ADT in urban areas. 

2. The roadway is a steep ascending grade to or through the crossing, sight 

distance in both directions is unrestricted in relation to maximum closing 

speed, and heavy vehicles use the crossing. 

A footnote in this joint document also states that “a crossing where there is 

insufficient time for any vehicle, proceeding from a complete stop, to safely 

traverse the crossing within the time allowed by maximum train speed, is an 

inherently unsafe crossing that should be closed.” 

ACTIVE DEVICES

An active highway-rail grade crossing is described as follows: 

All highway-rail grade crossings equipped with warning and/or traffic 

control devices that gives warning of the approach or presence of a 

train.

Due to the variables which should be considered, an engineering and traffic 

investigation is required to determine the specific application of active devices at 

any given highway-rail grade crossing. Guidance is provided in the following 

sections for the application of the many active traffic control system devices 

available for grade crossing design, in addition to various median treatments that 

can supplement these devices. The following is a list of active devices that can 

be considered for use at a highway-rail grade crossing. The first four commonly 

found at many grade crossings are designated as “standard devices.” 

STANDARD ACTIVE DEVICES

Flashing-Light Signal

A standard flashing-light signal consists of two red lights in a horizontal line 

flashing alternately at approaching highway traffic. At a crossing with highway 

traffic approaching in both directions, flashing-lights are installed facing oncoming 

traffic in a back-to-back configuration in accordance with the MUTCD. The 

support used for the lights should also include a standard crossbuck sign and, 

where there is more that one track, an auxiliary “multiple tracks” R15-2 sign. 

Back lights may be eliminated with one-way highway traffic, based on 

engineering judgment. An audible control device may be included. 

20 
Cantilever Flashing-Light Signal 

This device supplements the standard flashing-light signal. Cantilever 

flashing-lights consist of an additional one or two sets of lights mounted over the 

roadway on a cantilever arm and directed at approaching highway traffic. 

Cantilevered lights provide better visibility to approaching highway traffic, 

particularly on multi-lane approaches. This device is also useful on high-speed 

two-lane highways, where there is a high percentage of trucks, or where 

obstacles by the side of the highway could obstruct visibility of standard mast 

mounted flashing-lights. An example is where the terrain or topography of the 

approaching highway is such that the sight of a roadside mounted signal light 

could not be readily seen by an approaching driver due to vertical or horizontal 

curves. 

Cantilever flashing-light signals may be mounted back-to-back and should 

also have an additional crossbuck added to the overhead structure, based on site 

conditions and engineering judgment. 

Automatic Gate

The automatic gate provides supplemental visual display when used with 

both road side mounted flashing-lights and cantilever flashing-light signals. The 

device consists of a drive unit and a gate arm. The drive mechanism can be 

mounted on flashing-light posts or cantilever pole supports, or on a stand-alone 

support. The gate arm is fully reflectorized on both sides with 45 degree 

diagonal red and white stripes and has at least three lights; the tip light is 

continuously lit and the others alternately flash when the gate is activated and 

lowered. When lowered, the gate should extend across approaching highway 

traffic lanes. Special consideration should be given to clearances for movement 

of the counter weight arm portion of the gate drive unit in a median and adjacent 

to sidewalk locations with pedestrians, particularly with the requirements of the 

Americans with Disabilities Act (ADA) of 1990. 

Additional Flashing-Light Signals

Additional approaches to active highway-rail grade crossings require 

additional flashing-light signals be directed at the approaching traffic. These 

lights can be mounted on existing flashing-light masts, extension arms, additional 

traffic signal masts, cantilever supports, in medians or other locations on the left 

side of the roadway. 

SUPPLEMENTAL ACTIVE DEVICES

Active Advance Warning Signs with Flashers 

A train activated advance warning sign (utilizing the W-10 sign) should be 

considered at locations where sight distance is restricted on the approach to a 

crossing, and the flashing-light signals cannot be seen until an approaching 

driver has passed the decision point (the distance to the track from which a safe 

21 
stop can be made).2

 Two yellow lights can be placed on the sign to warn drivers 

in advance of a crossing where the control devices are activated. The 

continuously flashing yellow “caution” lights can influence driver speed and/or 

provide warning for stopped vehicles ahead. An Advisory Speed Plate sign 

indicating the safe approach speed also should be posted with the sign. 

If the advance flashers are connected to the railroad control circuitry, and 

only flash upon the approach of a train, they should be activated prior to the 

control devices at the crossing so that a driver would not pass a dark flasher and 

then encounter an activated flashing-light at the crossing. (Track circuits may 

need to be revised to handle this.) A few States use a supplementary message 

such as TRAIN WHEN FLASHING. In order to allow the traffic queue at the 

crossing time to dissipate safely, the advance flashers should continue to operate 

for a period of time after the active control devices at the crossing deactivate, as 

determined by an engineering study. 

If such an advance device fails, the driver would not be alerted to the 

activated crossing controls. If there is concern for such failure, some agencies 

use a passive, RAILROAD SIGNAL AHEAD sign to provide a full time warning 

message. The location of this supplemental advance warning sign is dependant 

on vehicle speed and geometric conditions of the roadway. 

Active Turn Restriction Signs

An active turn restriction sign (blank-out sign with internal illumination) 

displaying “No Right Turn” or “No Left Turn” (or appropriate international symbol) 

should be used in the following instances; on a parallel street within 15 m (50 ft) 

of the tracks where a turning vehicle from that parallel street could proceed 

around lowered gates; at a signalized highway intersection, where traffic signals 

at a nearby highway intersection are interconnected and preempted by the 

approach of the train, and all existing turn movements toward the grade crossing 

should be prohibited. These signs shall be visible only when the restriction is in 

effect. 

MEDIAN SEPARATION

Despite the dangers of crossing in front of oncoming trains, drivers continue 

to risk lives and property by driving around crossing gates. At many crossings a 

driver is able to cross the center line pavement marking and drive around a gate 

with little difficulty. The numbers of crossing gate violations can be reduced by 

restricting driver access to the opposing lanes. Highway authorities have 

implemented various median separation devices, which have shown a significant 

reduction in the number of vehicle violations at crossing gates. 

 2 Manual on Uniform Traffic Control Devices For Streets and Highways - 

2000 Edition. FHWA. Sections 2C.26 and 4K.01. Official website is 

http://mutcd.fhwa.dot.gov or 202-289-0222 

22 
 

There are limitations common to the use of any form of traffic separation at 

highway-rail grade crossings. These include restricting access to intersecting 

streets, alleys and driveways within the limits of the median and possible adverse 

safety effects. The median should be designed to allow vehicles to make left 

turns or U-turns through the median where appropriate, based on engineering 

judgment and evaluation. 

BARRIER WALLS SYSTEMS

Concrete barrier walls and guardrails generally prevent drivers from crossing 

into opposing lanes throughout the length of the installation. In this sense they 

are the most effective deterrent to crossing gate violations. But, the road must 

be wide enough to accept the width of the barrier and the appropriate end 

treatment.3

 Sight restrictions for vehicles with low driver eye heights and any 

special need for emergency vehicles to make a U-turn maneuver should be 

considered (but not for the purpose of circumventing the traffic control devices at 

the crossing). Installation lengths can be more effective if they extend beyond a 

minimum length of 46 m (150 ft). 

WIDE RAISED MEDIANS

Curbed medians generally range in width from 1.2 to more than 30 m (4 - 

100 ft). While not presenting a true barrier, wide medians can be nearly as 

effective since a driver would have significant difficulty attempting to drive across 

to the opposing lanes. The impediment becomes more formidable as the width of 

the median increases. A wide median, if attractively landscaped, is often the 

most aesthetically pleasing separation method. 

Drawbacks to implementing wide raised medians include availability of 

sufficient right-of-way, and maintenance of surface and/or landscape. Additions 

such as trees, flowers and other vegetation higher than .9 m (3 ft) above the 

roadway can restrict the drivers' view of approaching trains. Maintenance can be 

expensive depending on the treatment of the median. Limitation of access can 

cause property owner complaints, particularly for businesses. Non-mountable 

curbs can increase total crash rate and severity of accidents when struck by 

higher speed vehicles (>64 km/h [40 mph]).4

NON-MOUNTABLE CURB ISLANDS

Non-mountable curb islands are typically six to nine inches in height and at 

least .6m (2 ft) wide, and may have reboundable, reflectorized vertical markers. 

3 Roadside Design Guide. American Association of State Highway and 

Transportation Officials (AASHTO). Washington D.C.; 1996, 

www.aashto.org, 202-624-5801 

4 Ibid. 

23 
Drivers have significant difficulty attempting to violate these types of islands 

because the six to nine inch heights cannot be easily mounted and crossed. 

There are some disadvantages to be considered. The road must be wide 

enough to accommodate a two foot median. The increased crash potential 

should be evaluated. AASHTO recommends special attention be given to high 

visibility if such a narrow device is used in higher speed (>64 km/h [40 mph]) 

environments. 5

 Care should be taken to assure that an errant vehicle cannot 

bottom-out and protrude into the oncoming traffic lane. Sight restrictions for low 

driver eye heights should be considered if vertical markers are installed. Access 

requirements should be fully evaluated, particularly allowing emergency vehicles 

to cross opposing lanes (but not for the purpose of circumventing the traffic 

control devices at the crossing). Paint and reflective beads should be applied to 

the curb for night visibility. 

MOUNTABLE RAISED CURB SYSTEMS 

Mountable raised curb systems with reboundable vertical markers present 

drivers with a visual impediment to crossing to the opposing traffic lane. The 

curbs are no more than six inches in height, less than twelve inches in width, and 

built with a rounded design to create minimal deflection upon impact. When used 

together, the mountable raised median and vertical delineators discourage 

passage. These systems are designed to allow emergency vehicles to crossopposing lanes (but not for the purpose of circumventing the traffic control 

devices at the crossing). Usually such a system can be placed on existing roads 

without the need to widen them. 

Because mountable curbs are made to allow emergency vehicles to cross, 

and are designed to deflect errant vehicles, they also are the easiest of all the 

barriers and separators to violate. Large, formidable vertical markers will inhibit 

most drivers. Care should be taken to assure that the system maintains its 

stability on the roadway with design traffic conditions, and that retro-reflective 

devices or glass beads on the top and sides of the curb are maintained for night 

visibility. Curb colors should be consistent with location and direction of traffic 

adjacent to the device. 

OTHER BARRIER DEVICES

FOUR-QUADRANT TRAFFIC GATE SYSTEMS

Four-quadrant gate systems consist of a series of automatic flashing-light 

signals and gates where the gates extend across both the approach and 

 5 A Policy on Geometric Design of Highways and Streets. American 

Association of State Highway Transportation Officials (AASHTO). 2001 

Edition., available at www.ite.org, or 202-289-0222 or www.aashto.org, 

202-624-5801 

 

24 
 

departure side of roadway lanes. Unlike two-quadrant gate systems, fourquadrant gates provide additional visual constraint and inhibit nearly all traffic 

movements over the crossing after the gates have been lowered. At this time, 

only a small number of four-quadrant gate systems have been installed in the 

U.S., and incorporate different types of designs to prevent vehicles from being 

trapped between the gates. 

VEHICLE ARRESTING BARRIER SYSTEM - BARRIER GATE

A moveable barrier system is designed to prevent the intrusion of vehicles 

onto the railroad tracks at highway-rail grade crossings. The barrier devices 

should at least meet the evaluation criteria for a NCHRP Report 350 (Test Level 

2) attenuator; 6

 stopping an empty: 4500-pound pickup truck traveling at 70 km/h 

(43 mph). However, it could injure occupants of small vehicles during higher 

speed impacts, and may not be effective for heavy vehicles at lower speeds. 

Two types of barrier devices have been tested and used in the U.S.; vehicle 

arresting barriers and safety barrier gates. 

The vehicle arresting barrier (VAB) is raised and lowered by a tower lifting 

mechanism. The VAB in the down position consists of a flexible netting 

across the highway approaches that is attached to an energy absorption 

system. When the netting is struck, the energy absorption system dissipates 

the vehicle=s kinetic energy and allows it to come to a gradual stop. This 

device was tested at three locations in the high-speed rail corridor between 

Chicago, IL and St. Louis, MO. 

The safety barrier gate is a movable gate designed to close a roadway 

temporarily at a highway-rail crossing. A housing contains electromechanical components that lower and raise the gate arm. The gate arm 

consists of three steel cables, the top and bottom of which are enclosed 

aluminum tubes. When the gate is in the down position the end of the gate 

fits into a locking assembly that is bolted to a concrete foundation. This 

device has been tested to safely stop a pickup truck traveling at 72 km/h (45 

mph) and has been installed in Madison, WI and Santa Clara County, CA. 

A barrier gate could also be applied in those situations requiring a positive 

barrier e.g., in a down position, closing off road traffic and opening only on 

demand. 

6

 National Cooperative Highway Research Program NCHRP Report 350. 

Recommended Procedures for the Safety Performance Evaluation of 

Highway Features. Transportation Research Board. National Research 

Council. Washington, DC: 1993, contact TRB at www.trb.org. 

25 
TRAIN DETECTION SYSTEMS

WARNING TIME AND SYSTEM CREDIBILITY

Reasonable and consistent warning times re-enforce system credibility. 

Unreasonable or inconsistent warning times may encourage undesirable driver 

behavior. Research has shown when warning times exceed 40-50 seconds, 

drivers will accept shorter clearance times at flashing lights, and a significant 

number will attempt to drive around gates.7

 Although mandated maximum 

warning times do not yet exist, efforts should be made to ensure traffic 

interruptions are reasonable and consistent without compromising the intended 

safety function of an active control device system’s design. Excessive warning 

times are generally associated with a permanent reduction in the class of track 

and/or train speeds without a concomitant change in the track circuitry and 

without constant warning time equipment. When not using constant warning train 

detection systems, track approach circuits should be adjusted accordingly when 

train speeds are permanently reduced. Another frequent cause of excessive 

warning times at crossings without constant warning time equipment is variable 

speed trains, e.g., inter-city passenger trains or fast commuter trains interspersed 

with slower freight trains. 

A major factor affecting system credibility is an unusual number of false 

activations at active crossings. Every effort should be made to minimize false 

activations through improvements in track circuitry, train detection equipment, 

and maintenance practices. A timely response to a system malfunction coupled 

with repairs made without undue delay can reduce credibility issues. Remote 

monitoring devices are an important tool. 

Joint study and evaluation is needed between the highway agency and 

railroad to make a proper selection of the appropriate train detection system. 

Train detection systems are designed to provide the minimum warning time 

for a crossing. In general, the MUTCD states that the system should provide for 

a minimum of 20 seconds warning time. When determining if the minimum 20 

seconds warning time should be increased, the following factors should be 

considered: 

• track clearance distances due to multiple tracks and/or angled crossings; 

(add one second for each 3 m [10 ft] of added crossing length in excess of 

10.7 m [35 ft]); 

• the crossing is located within close proximity of a highway intersection 

controlled by STOP signs where vehicles have a tendency of stopping on 

the crossing; 

 7 Warning Time Requirements at Railroad-Highway Grade Crossings with 

Active Traffic Control. Report No. FHWA SA-91-007, Federal Highway 

Administration. Washington, DC: February 1991, www.fhwa.dot.gov.

26 
• the crossing is regularly used by long tractor-trailer vehicles; 

• the crossing is regularly used by vehicles required to make mandatory 

stops before proceeding over the crossing (e.g. school buses and 

hazardous materials vehicles); 

• the crossing’s active traffic control devices are interconnected with other 

highway traffic signal systems; 

• provide at least 5 seconds between the time the approach lane gates to 

the crossing are fully lowered and when the train reaches the crossing, per 

49 CFR Part 234; 

• the crossing is regularly used by pedestrians and non-motorized 

components; 

• where the crossing and approaches are not level and ; 

• where additional warning time is needed to accommodate a four-quadrant 

gate system. 

INTERFERENCE / INTEGRITY OF ACTIVE TRAFFIC CONTROL DEVICE 

SYSTEMS

Interference with normal functioning of an active control device system 

diminishes the driver’s perception of the integrity of the system. Interference can 

result from, but is not limited to, trains, locomotives or other railroad equipment 

standing within the system’s approach circuit, and testing or performing work on 

the control device systems or on track and other railroad systems or structures. 

The integrity of the control device system may be adversely affected if proper 

measures are not taken to provide for safety of highway traffic when such work is 

underway. It is important that Railroad employees are familiar with Federal 

regulations and railroad procedures which detail measures to be taken prior to 

commencing activities, which might interfere with track circuitry. 

TYPE OF DETECTION SYSTEM

DC, AC-DC or AFO Grade Crossing Island and Approach Circuits:

These basic train detection circuits use a battery or transmitter at one end of 

a section of track and a relay, receiver or diode at the other end. A train on the 

section of the affected track will shunt the circuit and de-energize the relay. This 

type of system will continue to operate until the train leaves the circuit. 

Motion Sensitive Devices (MS)

A type of train detection (control) system for automatic traffic control devices 

that has the capability of detecting the presence and movement of a train within 

the approach circuit of a crossing. MS devices will activate the traffic control 

devices at the crossing for all trains located within the approach circuit that are 

moving toward the crossing, regardless of train speed. If a train stops within the 

approach circuit before reaching the crossing, the traffic control devices will 

deactivate until the train resumes motion toward the crossing, but will remain 

deactivated if the train retreats beyond the detection circuit. 

27 
Constant Warning Time (CWT) Systems 

A constant warning time system has the capability of sensing a train as it 

approaches a crossing, measuring its speed and distance from the crossing, and 

activating the traffic control devices to provide the desired warning time. Traffic 

control systems equipped with CWT provide relatively uniform warning times 

where train speeds vary and trains do not accelerate or decelerate within the 

approach circuits once the devices have activated. Trains may perform low 

speed switching operations beyond 213 m (700 ft) from a crossing without 

causing the crossing devices to unnecessarily activate. This reduces or 

eliminates excess gate operation that in turn, causes unnecessary delays to 

highway traffic. Like motion sensitive systems, if a train stops within the 

approach circuit before reaching the crossing the traffic control devices will 

deactivate. 

RAILROAD TRAIN DETECTION TIME AND APPROACH LENGTH 

CALCULATIONS

It should be noted that even when “constant warning devices” are used, the 

calculated arrival time of the train at the crossing is based on the instantaneous 

speed of the train as it enters the crossing circuit. Once the calculation is made, 

changes in train speed will change train arrival time at the crossing and 

correspondingly reduce (or increase) the elapsed warning time at the crossing. 

This factor must be considered at a crossing interconnected to a nearby highway 

traffic signal utilizing either a simultaneous or advance preemption sequence. 

Design information about railroad interconnection circuits and approach 

length calculations can be found in the American Railway Engineering and 

Maintenance-of-Way Association (AREMA) Signal Manual8

, Manual Part 3.1.10, 

Recommended Functional/Operating Guidelines for Interconnection Between 

Highway Traffic Signals and Highway - Rail Grade Crossing Warning Systems; 

and Manual Part 3.3.10, Recommended Instructions for Determining Warning 

Time and Calculating Minimum Approach Distance for Highway-Rail Grade 

Crossing Warning Systems. 

PREEMPTION/INTERCONNECTION:

WHEN TO INTERCONNECT

The guidance in the MUTCD states: “When a highway-rail grade is equipped 

with a flashing-light signal system and is located within 60 m (200 ft) of an 

intersection or mid-block location controlled by a traffic control signal, the traffic 

control signal should be provided with preemption in accordance with Section 

4D.13.” Recent studies indicate that when designing for the installation of a new 

traffic control signal substantially beyond 60 m (200 ft) (possibly 152-305m [500-

 

8 American Railway Engineering and Maintenance-of-Way Association (AREMA) Signal Manual,

Manual Part 3.1.10 is available at the following URL: http://www.arema.org/pubs/pubs.htm

28 
1000 ft]) of a highway-rail grade crossing, an estimate of the expected queue 

length should be performed. For estimation purposes, a 95% probability level 

should be used. If the resulting expected queue length is equal to or greater than 

the available storage distance, consideration should be given to interconnecting 

the traffic control signal with the active control system of the railroad crossing and 

providing a preemption sequence. Guidance on estimating queue length is 

available in the article, “Design Guidelines for Railroad Preemption at Signalized 

Intersections,” ITE Journal, February 1997. Guidance on the design of 

preemption operation is available in Preemption of Traffic Signals At or Near 

Railroad Grade Crossings with Active Warning Devices, #RP-025A, Institute of 

Transportation Engineers, 1997 www.ite.org or 202-289-0222; and the 

Implementation Report of the USDOT Grade Crossing Safety Task Force, June 

1, 1997, U.S. Department of Transportation, www.fhwa.dot.gov. The 

Implementation Report is an excellent source of definitions. 

FACTORS TO CONSIDER

Joint Agency Coordination

Close coordination between the highway agency and the railroad company is 

required when interconnecting a traffic signal with active railroad traffic control 

devices. In order to properly design the highway-rail preemption system, both 

the railroad company and the highway agency should understand how each 

system operates. An engineering study should be conducted at each 

interconnected location to 

determine the minimum preemption warning time necessary to adequately clear 

traffic from the crossing in the event of an approaching train. Factors that need 

to be considered when calculating this time are equipment response and 

programmed delay times, minimum traffic signal green times, traffic signal 

vehicular and pedestrian clearances, queue clearance times and train/vehicle 

separation time. 

Extended Advance Warning Times

Whenever it becomes necessary at gated crossings to provide design 

advance warning times in excess of 45 seconds, whether for traffic signal 

preemption or other purposes, consideration should be given to including 

supplemental median treatments to discourage drivers from attempting to 

circumvent the gates. 

Second Train Circuitry at Multiple Track Crossings

At multiple track crossings, “second train” circuitry can be considered as part 

of the control network. This circuitry is intended to detect a second train 

approaching the crossing, but outside the normal warning time approach circuit. 

For instance, the normal approach circuit may provide 25 seconds warning but 

the second-train circuit may look an additional 10 seconds. If a train activates a 

train activates the traffic control devices AND a second train is detected within 

the 35-second circuit, the gates will be held down for the second train and the 

29 
traffic signals remain preempted. (Also see Traffic Signal Controller Re-Service 

Considerations in the Preemption/Interconnection Appendix.) 

Diagonal Railroad Crossing 

Both Highway Approaches to 

the Intersection

Where the railroads run 

diagonally to the direction of the 

highway, it is probable that the 

railroad may cross two highway 

approaches to an 

interconnected intersection. 

When this situation occurs, it is 

normally necessary to clear out 

traffic on both roadways prior to 

the arrival of the train, requiring 

approximately twice the 

preemption time computed for 

one approach. It is also 

normally required to have both 

railroad active traffic control 

device systems designed to operate concurrently. This is needed to prevent the 

interconnected traffic signals and railroad active control devices from falling out 

of coordination with each other which otherwise can occur under certain types of 

train movements or when one of the two crossings experiences a false signal 

activation prior to an actual train movement. When the railroad control devices 

activate, traffic leaving the intersection and approaching either crossing may 

queue back into the intersection and block traffic if there is not adequate storage 

for those vehicles between the crossing and the intersection. Traffic turning at 

the intersection toward the other crossing may also be unable to proceed due to 

stopped traffic. 

When this occurs, utilization of advance preemption together with a hybrid 

design may help alleviate this problem. The hybrid design could consist of 

delaying the activation of the railroad devices facing vehicles leaving the 

intersection and approaching both crossings to help vehicles clear out of the 

intersection during the preemption sequence. 

Pre-Signals 

Pre-signals control traffic approaching the highway-rail grade crossing toward 

the nearby highway intersection, and are operated as part of the highway 

intersection traffic signal system. Their displays are integrated into the railroad 

preemption program. A diagram of a pre-signal is shown as Figure 4. 

30 
Figure 4

This figure depicts the location of a pre-signal at an automatic gate crossing. In 

the foreground of the figure is the away-going side of a divided highway. The 

road crosses a railroad track and a little further, intersects another road. At the 

intersection of the two roads, there is a traffic-control signal. The crossing is 

equipped with lights and an automated crossarm. Prior to the railroad crossing is 

another traffic-control signal and a double white line where vehicles are to stop. 

The signal and lines are designed to prevent a line of vehicles forming at the 

highway-highway intersection that would back up onto the railroad tracks. On 

either side of the road at the double white line is a sign that reads “STOP HERE 

ON RED,” with and arrow pointing to the double white line. 

An engineering study should be made to evaluate the various elements 

involved in a pre-signal. These are summarized as follows. 

Where the highway intersection is less than 15m (50 ft) from the 

highway-rail crossing (23m [75 ft] for a roadway regularly used by multiunit vehicles), pre-signals should be considered. Where the clear 

storage distance is greater than 23 m (75 ft), pre-signals could be used, 

subject to an engineering study determining that the queue extends into 

the track area. 

Without pre-signals at highway-rail grade crossings, drivers may focus 

on the downstream highway traffic signal indications rather than the 

flashing-light signals located at the grade crossing. This type of driver 

behavior is especially undesirable during the beginning of the preemption 

sequence when the downstream traffic signals are typically green (in 

order to clear queued vehicles off the tracks) and the flashing-light 

signals are activated. 

Driver behavior at crossings equipped with pre-signals is modified 

because the driver stops at the railroad stop line even when a train is not 

approaching. By providing a consistent stopping location, with or without 

the presence of a train, the driver will not become confused as to a safe 

location to stop when a train is approaching. 

Where geometric considerations in advance of the crossing complicate 

the installation of a pre-signal on a separate support in front of the 

railroad signal, the placement of railroad flashing-light signals and traffic 

signals on the same support should be considered to reduce visual 

clutter and to increase driver visibility of the pre-signals. A written 

agreement between the highway agency and railroad may be required. 

The pre-signal phase sequencing should be progressively timed with an 

offset adequate to clear vehicles from the track area and downstream 

intersection. Vehicles that are required to make a mandatory stop (e.g., 

31 
school buses, vehicles hauling hazardous materials, etc.) should be 

considered when determining the amount of time for the offset to ensure 

that they will not be forced to stop in the clear storage area. 

For highway-rail grade crossings equipped with a pre-signal and clear 

storage distance less than 15 m (50 ft), (23 m [75 ft] for a roadway 

regularly used by multi-unit vehicles), a clear zone between the crossing 

and the downstream intersection may be diagonally striped to delineate 

the clear storage area. 

The downstream traffic signal at the highway intersection controlling the 

same approach as the pre-signal should be equipped with programmable 

visibility indications or louvers. The downstream heads should only be 

visible from within the down stream intersection to the driver eye location 

of the first vehicle behind the pre-signal stop bar. Design of the visibility 

limited indications is quite complex and should consider a range of driver 

eye heights for the various vehicles expected on the roadway. 

Long Distance between the Highway-Rail Crossing and the Highway 

Intersection

In cases where the crossing is located far from the highway intersection -- up 

to 305 m (1000 ft), the necessary minimum preemption warning time may be very 

high and in turn may require very long approach circuits along the tracks in order 

to provide such a time. Long track circuits can become extremely complex and 

expensive to implement, especially if located in an area where there are several 

adjacent crossings with overlapping track circuits, switching spurs, railroad 

junctions or commuter rail stations which could affect train operating speeds 

within the detection circuit. In addition, excessive preemption times may have 

detrimental effects on traffic flows within the vicinity of the crossing and may 

cause other problems such as traffic backing up along a route parallel to the 

crossing and backing up through another adjacent interconnected intersection. 

These are just a few factors to consider with a long distance interconnection. 

Queue Cutter Flashing-light Beacon

An alternative to interconnecting the two traffic control devices may be the use of 

an automated Queue Cutter Flashing-light Beacon upstream of the highway-rail 

grade crossing. They may be utilized in conjunction with DO NOT STOP ON 

TRACKS (R8-8) as stated in the MUTCD signs. Such beacons can be activated 

by an induction loop on the departure side of the highway-rail grade crossing that 

detects a growing queue between the crossing and the distant highway 

intersection. If the beacons are activated only when the traffic signals on that 

approach are not green, they can be more effective as opposed to flashing all the 

time. 

These are some of the many factors that should be considered when 

interconnecting an active traffic control device at a highway-rail grade crossing to 

32 
a nearby highway traffic signal. A separate Preemption/Interconnection appendix 

is included with this report to provide further explanation of this very complex 

subject. However, it is not the intent of this document to serve as a primer for 

this very complicated topic. It cannot be emphasized enough that design, 

construction, operation and maintenance of this type of system requires expert 

knowledge and full cooperation between highway and railroad authorities. Other 

special conditions are discussed in the following section. 

Also See Appendix for additional information 

OTHER SPECIAL CONDITIONS

POTENTIAL QUEUING ACROSS TRACKS

Where queuing across a highway-rail grade crossing is occasioned by a 

nearby highway intersection that is not equipped with a traffic signal, the traffic 

engineer has a number of options including: 

1) Install a DO NOT STOP ON TRACKS sign; 

2) Install an automated Queue Cutter Flashing-light Beacon (see prior 

discussion in “Factors to Consider”); and/or; 

3) Install a traffic signal with railroad preemption at the highway/highway 

intersection. 

Queues extending over the highway-rail grade crossing could be considered 

a possible need for the installation of a traffic signal at the nearby highway 

intersection. However, the third option needs to be considered very carefully 

considering the harmful effects of an otherwise unwarranted traffic signal. 

TRAIN AND LIGHT RAIL TRANSIT (LRT) ACTIVATED HIGHWAY TRAFFIC 

SIGNALS

Urban city streets often pose a special case for the application of active 

grade crossing traffic control devices. Slow speed switching moves and mixeduse light rail transit (LRT) operations are often controlled by traffic signals. In 

such cases, traffic signal heads must be clearly visible to the train operator. 

Trains must stop short before entering these intersections. Train detection can 

be accomplished by the use of island track circuits, key selector switches, 

inductive loops, train to way-side communications and other technologies. 

Where LRT vehicles move within the street median or through the 

intersection of two or more city streets, and where train operating speeds and 

sight distances are consistent with safe stopping distances, the train may operate 

through these intersections controlled by traffic signal indications without 

stopping. In such cases, special transit signal aspects, which clearly indicate 

traffic signal controlled right-of-way, must govern train moves. Special transit 

indications may also provide information concerning track alignment to the transit 

operator. Automatic train stops and other train control devices may be used to 

enforce a train=s compliance with the signal indication. Where special train 

33 
aspects are present and safe stopping distance is assured, transit vehicles may 

utilize train to way-side communications, inductive loops, cantenary detector 

switches or other forms of detection to activate the traffic signals. Great care 

should be exercised in the location of special train indicators to avoid confusion 

to drivers approaching the intersection. Programmed heads and special aspects 

are helpful in this regard. 

(SECOND) TRAIN COMING ACTIVE WARNING SIGN

Train detection systems can also be used to activate a “2nd Train Coming” 

supplemental warning sign. This sign is used on a limited basis, normally near 

commuter stations where multiple tracks and high volumes of pedestrian traffic 

are present. The sign will activate when a train is located within the crossing’s 

approach circuits and a 2nd train approaches the crossing. It is also being 

evaluated at multiple track highway-rail grade crossings as a supplement to 

automatic gates. (Since this sign is not currently in the MUTCD, any jurisdictions 

wishing to use symbols to convey any part of this message, must request 

permission to experiment from the FHWA.) 

PEDESTRIAN AND BICYCLIST CONSIDERATIONS

Non-motorist-crossing safety should be considered at all highway-rail grade 

crossings, particularly at or near commuter stations and at non-motorist facilities, 

such as bicycle/walking trails, pedestrian only facilities, and pedestrian malls.9

Passive and active devices may be used to supplement highway related 

active control devices to improve non-motorist safety at highway-rail crossings. 

Passive devices include fencing, swing gates, pedestrian barriers, pavement 

markings and texturing, refuge areas and fixed message signs. Active devices 

include flashers, audible active control devices, automated pedestrian gates, 

pedestrian signals, variable message signs and blank out signs. 

These devices should be considered at crossings with high pedestrian traffic 

volumes, high train speeds or frequency, extremely wide crossings, complex 

highway-rail grade crossing geometry with complex right-of-way assignment, 

school zones, inadequate sight distance, and/or multiple tracks. All pedestrian 

facilities should be designed to minimize pedestrian crossing time and devices 

should be designed to avoid trapping pedestrians between sets of tracks. 

Guidelines for the use of active and passive devices for Non-motorist Signals

and Crossings are found in section 10D of Part 10 of the MUTCD. 

 9

 Traffic Control Devices Handbook. Institute of Transportation Engineers. 

Washington, D.C.: 2001. Section 13.2.12, Railroad and Light Rail Transit 

Grad Crossings, www.ite.org or 202-289-0222.

34